ABSTRACT The identification of a maturational spurt during normal skeletal development is of critical biomedical and public health importance because it will: (1) improve clinical treatment timing for children suffering from skeletal disorders, and (2) provide a more detailed understanding of human skeletal biology for the future biomedical field. Fluctuations in the tempo of skeletal maturation may provide greater prognostic value than other ontogenetic parameters. These fluctuations, including a potential maturational ?spurt,? similar to the pubertal growth spurt, have yet to be comprehensively characterized. Aim 1 of the proposed F31 will use existing data on skeletal age collected by the Sponsor to examine tempo changes in skeletal maturation and to elucidate the relationship between ontogenetic parameters of the maturational spurt with known parameters of the pubertal growth spurt. Aim 2 will provide refined skeletal maturity indicator grades predictive of distinct parameters of the pubertal growth spurt and the maturational spurt. This aim will include the collection of new skeletal maturity indicator data by the applicant. Because the timing of skeletal maturity is influenced by racial and/or ethnic background, Aim 3 will focus on characterizing the tempo of maturation in children of African American, Asian American, and Hispanic descent. These Aims will be accomplished by leveraging existing longitudinal data from two longitudinal studies of childhood and incorporating a variety of multi-level, repeated-measure modeling techniques, including polynomial modeling and ordinal logistic regression. The results from the proposed analyses will provide clinicians with improved skeletal maturity assessment tools that will lead to optimization of individualized pediatric treatment timing and improved quality of life in patients with skeletal disorders.